Antioxidative effect of essential oils of Thymbra spicata on palm and corn oils

In this study, Rancimat Method, which is one of the Accelerated Shelf-Life Test(ASLT) method, was used to determine the effect of Thymbra spicata extract on theoxidative stability of corn oil and palm oil. For the comparison of the effect ofThymbra spicata extract butylated hydroxyltoluene (BHT) was used as a standardantioxidant. During the ASLT, the conductivity was followed at three temperatures,90, 100 and 120oC, with the addition of Thymbra spicata essential oils and BHT tocorn and palm oils. The concentrations of Thymbra spicata essential oils and BHTused were in the range of 1.39-5.49 mg ml-1 and 0.014-2.4 mg ml-1 respectively.The same concentrations of both antioxidants used were also added into corn andpalm oils to observe the chenge in peroxide value under storage temperatures of 15,25 and 35oC.2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging test was used for thedetermination of scavenging effect of Thymbra spicata extract. BHT was used as thestandard antioxidant. The scavenging effect of Thymbra spicata extract was found tobe 75.7 % while scavenging effect of BHT was found to be 73.7 %. Scavengingeffect of Thymbra spicata was found to be significant compared to BHT.It was observed that the corn oil was less stable to oxidation than palm oil. Theaddition of Thymbra spicata and BHT increased the induction times of corn oil andpalm oil at each studied temperature. As the temperature decreased the inductiontime increased. Thymbra spicata extract was more effective than BHT.